I had an SX20 IS and returned it. Excessive fringing (CA) and clipped highlights. I'd suggest avoiding Canon for this particular class of camera despite their bodies being nicely built and having lots of nice features. The SX30 apparently has improved image quality, but I remain unconvinced.

My best experiences with compacts have been with Panasonics. If you really want a Canon, pick the S95 provided you can live with a bit less zoom range.